Compact Mass Spectrometer

Abstract

A miniature mass spectrometer is disclosed comprising an atmospheric pressure ionisation source and a first vacuum chamber having an atmospheric pressure sampling orifice or capillary, a second vacuum chamber located downstream of the first vacuum chamber and a third vacuum chamber located downstream of the second vacuum chamber. An ion detector is located in the third vacuum chamber. A first RF ion guide is located within the first vacuum chamber and a second RF ion guide is located within the second vacuum chamber. The ion path length from the atmospheric pressure sampling orifice or capillary to an ion detecting surface of the ion detector is ≦400 mm. The mass spectrometer further comprises a tandem quadrupole mass analyser, a 3D ion trap mass analyser, a 2D or linear ion trap mass analyser, a Time of Flight mass analyser, a quadrupole-Time of Flight mass analyser or an electrostatic mass analyser arranged in the third vacuum chamber. The product of the pressure P1 in the vicinity of the first RF ion guide and the length L1 of the first RF ion guide is in the range 10-100 mbar-cm and the product of the pressure P2 in the vicinity of the second RF ion guide and the length L2 of the second RF ion guide is in the range 0.05-0.3 mbar-cm.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority from and the benefit of United Kingdom patent application No. 1309768.8 filed on 31 May 2013, United Kingdom patent application No. 1309770.4 filed on 31 May 2013 and European patent application No. 13170146.8 filed on 31 May 2013. The entire contents of these applications are incorporated herein by reference.BACKGROUND TO THE PRESENT INVENTION[0002]The present invention relates to a mass spectrometer and a method of mass spectrometry. The preferred embodiment relates to a compact or miniature mass spectrometer in conjunction with an Atmospheric Pressure Ionisation (“API”) ion source.[0003]Conventional mass analysers are normally unable to operate at or near atmospheric pressure and so are located within a vacuum chamber that is evacuated to a low pressure. Most commercial mass analysers operate at a vacuum level of 1×10−4 mbar or lower.[0004]Mass spectrometers with Atmospheric Pressure Ionisation (“API”) i...

AI Technical Summary

Benefits of technology

The patent text describes a new design for a miniature mass spectrometer that operates at a higher pressure-length value (0.1-0.3 mbar-cm) compared to the known spectrometer (0.01 mbar-cm). This higher pressure-length value allows for the ions to be accelerated and cooled in a way that ensures they have a small spread of ion energies. This results in improved performance of the miniature mass spectrometer.

Problems solved by technology

A single orifice between the ion source at atmospheric pressure and the mass analyser is the most direct method but is generally impractical since either the atmospheric pressure orifice needs to be made so small that the number of ions transmitted into the vacuum chamber will be very low (thereby severely restricting the sensitivity of the instrument) or alternatively the mass spectrometer requires an impractically large vacuum pump.

However, replacing a conventional sized orifice with a smaller orifice is problematic since the smaller orifice will have a detrimental effect upon the sensitivity of the instrument.

Reducing the sensitivity of the instrument will limit the usefulness of the miniature mass spectrometer and make it less commercially viable.

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